Genetic diversity and structuring in the arapaima (Osteoglossiformes, Osteoglossidae) population reveal differences between the Amazon and the Tocantins-Araguaia basins

Abstract

Arapaima is a widely-distributed fi sh of enormous economic importance in the Amazon region. In the present study, a total of 232 specimens were sampled, 121 from fi ve sites in the Amazon basin and 111 from fi ve sites in the Tocantins-Araguaia basin. The analyses investigated fragments of the Cytochrome b, Control Region, Cytochrome Oxidase I, NADH dehydrogenase subunit 2 and seven loci microsatellites. The analyses revealed the existence of two mitochondrial lineages within the general area, with no haplotypes shared between basins, and genetic variability signifi cantly higher in the Amazon than in the Tocantins-Araguaia basin. Two divergent, but sympatric mitochondrial lineages were found in the Amazon basin, but only a single lineage in the Tocantins-Araguaia basin. The existence of these two mitochondrial lineages indicates that past events, probably occurring during the Pleistocene, resulted in the separation of the populations of this species and molded its evolutionary history, which is refl ected directly in its mitochondrial DNA. The analysis of the arapaima population structure identifi ed distinct levels of diversity within the distribution of the species, indicating specifi c geographic regions that will require special attention for the development of conservation and management strategies.

Genomic differentiation with gene flow in a widespread Amazonian floodplain‐specialist bird species

“…This is reflected in the X. obsoletus population structure as well, although, interestingly, in more recent times than the split estimated between western and central Amazonian populations (see T 2 in Table 3). Other widespread floodplain-associated Amazonian lineages exhibiting significant genetic differentiation in the Tocantins drainage are the river dolphins of the genus Inia (Hrbek et al, 2014) and the Arapaima fishes (Nogueira et al, 2020). Details on the dynamics of past connections between the Tocantins and the Amazon´s floodplains have yet to be clarified, but the Tocantins floodplain is known to have had a very recent dynamic history and high loads of Quaternary sediments (Jesus et al, 2020), which have impacted the extent and distribution riverine-created habitats.…”